There is proposed an active sound effect generating apparatus (hereinafter also referred to as an “active sound control apparatus (ASC apparatus)”) which detects an acceleration-deceleration operation by a driver and generates in a vehicle interior via an in-vehicle speaker a sound effect in accordance with the amount of acceleration-deceleration (for example, refer to Japanese Unexamined Patent Application Publication No. 2009-031428 and Japanese Unexamined Patent Application Publication No. 2013-167851).
In Japanese Unexamined Patent Application Publication No. 2009-031428, the amplitude of a control signal Sc is set by adjusting the amplitudes of reference signals Sr1, Sr2, and Sr3 in accordance with an amount of change in rotational frequency Δaf [Hz/sec], which is a time differential value of an engine rotational frequency fe [Hz], and an accelerator opening degree Aor [%] (summary).
In Japanese Unexamined Patent Application Publication No. 2013-167851, a first gain GΔaf based on the amount of change in rotational frequency Δaf, which is the time differential value of the engine rotational frequency fe, and a shift position Ps is set (FIG. 1 and paragraph [0038]). In addition, a second gain Gfe based on the engine rotational frequency fe is set (paragraph [0039]). Furthermore, a third gain Gap based on an accelerator opening degree θap is set (paragraph [0040]). The product of the second gain Gfe and the third gain Gap is calculated and the calculated product is added to the first gain GΔaf to calculate a fourth gain Gcom (paragraphs [0044] and [0045]). A control signal Sc2 (an amplitude adjustment control signal) is generated using the fourth gain Gcom (paragraph [0046]).
Vehicles that use continuously variable transmissions (CVTs) as transmissions and electric vehicles (for example, hybrid vehicles and strict battery-powered vehicles) that use motors as driving sources have been in widespread use in recent years.
In the case of a typical vehicle including a CVT, the variation in the engine rotational frequency may not follow the operation of an accelerator pedal on a road, such as a slope, even if the accelerator pedal is depressed by the driver. For example, when the accelerator pedal is suddenly depressed, a situation may occur in which the shift transmission by the CVT does not follow the operation of the accelerator pedal, the engine rotational frequency is increased first, and the vehicle speed is not immediately increased.
In such a case, the vehicle speed may not follow the amount of change in rotational frequency or the amount of change in the accelerator opening degree in the configuration in which the amplitude of the sound effect is adjusted in accordance with the amount of change in rotational frequency and the accelerator opening degree, as in Japanese Unexamined Patent Application Publication No. 2009-031428 and Japanese Unexamined Patent Application Publication No. 2013-167851, thereby causing the driver to be concerned.
In electric vehicles, an engine is not as a driving source. In hybrid vehicles, there are cases in which the engine is stopped and the vehicle runs using only a motor. In the vehicles described above which do not use an engine at all or use an engine only temporarily as a driving source, it is difficult to apply the technologies in Japanese Unexamined Patent Application Publication No. 2009-031428 and Japanese Unexamined Patent Application Publication No. 2013-167851 in which the engine rotational frequency and the amount of change in rotational frequency, which is the time differential value of the engine rotational frequency, are used.
It is also desirable to resolve the above problems in the vehicles that use an engine without provided with the CVT considering common usage of the ASC apparatuses among several types of vehicles.